Ground vehicles employ electric energy storage devices, including both low-voltage devices, e.g., lead-acid batteries, and high-voltage devices, e.g., lithium-ion devices. The low-voltage energy storage devices may be employed to supply electric power for engine starting and low-voltage electrical loads, e.g., lighting, HVAC, infotainment and other on-vehicle loads. The high-voltage energy storage devices may be employed to supply electric power to electric motor/generators for vehicle propulsion and tractive effort. Vehicle owners are known to park and store vehicles for extended periods of time, e.g., for winter-related storage. On-board parasitic loads may reduce charge state of the low-voltage energy storage devices and the high-voltage energy storage devices.